Detection: Get-ForestTrust with PowerShell Script Block

Updated Date: 2024-11-13 ID: 70fac80e-0bf1-11ec-9ba0-acde48001122 Author: Michael Haag, Splunk Type: TTP Product: Splunk Enterprise Security

Description

The following analytic detects the execution of the Get-ForestTrust command from PowerSploit using PowerShell Script Block Logging (EventCode=4104). This method captures the full command sent to PowerShell, providing detailed visibility into potentially suspicious activities. Monitoring this behavior is crucial as it can indicate an attempt to gather domain trust information, which is often a precursor to lateral movement or privilege escalation. If confirmed malicious, this activity could allow an attacker to map trust relationships within the domain, facilitating further exploitation and access to sensitive resources.

Search

1`powershell` EventCode=4104 ScriptBlockText = "*get-foresttrust*" 
2| stats count min(_time) as firstTime max(_time) as lastTime by EventCode ScriptBlockText Computer UserID 
3| rename Computer as dest 
4| rename UserID as user 
5| `security_content_ctime(firstTime)` 
6| `security_content_ctime(lastTime)` 
7| `get_foresttrust_with_powershell_script_block_filter`

Data Source

Name	Platform	Sourcetype	Source
Powershell Script Block Logging 4104	Windows	`'xmlwineventlog'`	`'XmlWinEventLog:Microsoft-Windows-PowerShell/Operational'`

Macros Used

Name	Value
powershell	`(source=WinEventLog:Microsoft-Windows-PowerShell/Operational OR source="XmlWinEventLog:Microsoft-Windows-PowerShell/Operational")`
get_foresttrust_with_powershell_script_block_filter	`search *`

get_foresttrust_with_powershell_script_block_filter is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Annotations

- MITRE ATT&CK

+ Kill Chain Phases

+ NIST

+ CIS

- Threat Actors

ID	Technique	Tactic
T1482	Domain Trust Discovery	Discovery
T1059.001	PowerShell	Execution

Exploitation

Installation

DE.CM

CIS 10

Default Configuration

This detection is configured by default in Splunk Enterprise Security to run with the following settings:

Setting	Value
Disabled	true
Cron Schedule	`0 * * * *`
Earliest Time	`-70m@m`
Latest Time	`-10m@m`
Schedule Window	`auto`
Creates Notable	Yes
Rule Title	`%name%`
Rule Description	`%description%`
Notable Event Fields	user, dest
Creates Risk Event	True

This configuration file applies to all detections of type TTP. These detections will use Risk Based Alerting and generate Notable Events.

Implementation

To successfully implement this analytic, you will need to enable PowerShell Script Block Logging on some or all endpoints. Additional setup here https://docs.splunk.com/Documentation/UBA/5.0.4.1/GetDataIn/AddPowerShell#Configure_module_logging_for_PowerShell.

Known False Positives

False positives may be present. Tune as needed.

Associated Analytic Story

Active Directory Discovery

Risk Based Analytics (RBA)

Risk Message:

Suspicious PowerShell Get-ForestTrust was identified on endpoint $dest$ by user $user$.

Risk Object	Risk Object Type	Risk Score	Threat Objects
user	user	12	No Threat Objects
dest	system	12	No Threat Objects

References

Detection Testing

Test Type	Status	Dataset	Source	Sourcetype
Validation	✅ Passing	N/A	N/A	N/A
Unit	✅ Passing	Dataset	`XmlWinEventLog:Microsoft-Windows-PowerShell/Operational`	`XmlWinEventLog`
Integration	✅ Passing	Dataset	`XmlWinEventLog:Microsoft-Windows-PowerShell/Operational`	`XmlWinEventLog`

Replay any dataset to Splunk Enterprise by using our replay.py tool or the UI. Alternatively you can replay a dataset into a Splunk Attack Range

Source: GitHub | Version: 5